Aqueous solution method for forming hydrodesulfurization catalyst

ABSTRACT

A method of making a hydrodesulfurization catalyst having nickel and molybdenum supported on activated carbon is specified. The hydrodesulfurization catalyst produced is mesoporous having an average pore diameter of 4-10 nm and a BET surface area of 250-500 m 2 /g. The utilization of the hydrodesulfurization catalyst in treating a hydrocarbon feedstock containing aromatic sulfur compounds (e.g. dibenzothiophene) to produce a desulfurized hydrocarbon stream is also provided.

BACKGROUND OF THE INVENTION Technical Field

The present disclosure relates to a method of makinghydrodesulfurization catalyst containing nickel and molybdenum and aprocess of utilizing the catalyst in hydrodesulfurization of ahydrocarbon feedstock.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Crude oil is a valuable source of energy and raw material for majorindustries worldwide. However, the presence of sulfur compounds such asthiophenes in crude oil precludes its application in fuel cells, leadsto environmental pollution, and increases refining costs due to catalystpoisoning and corrosion of refining equipment [Y. Wang, F. H. Yang, R.T. Yang, J. M. Heinzel, and A. D. Nickens, “Desulfurization ofhigh-sulfur jet fuel by π-complexation with copper and palladium halidesorbents,” Ind. Eng. Chem. Res., vol. 45, no. 22, pp. 7649-7655, 2006;C. Song, “An overview of new approaches to deep desulfurization forultra-clean gasoline, diesel fuel and jet fuel,” Catal. Today, vol. 86,no. 1-4, pp. 211-263, 2003; and W. Li, J. Liu, and D. Zhao, “Mesoporousmaterials for energy conversion and storage devices,” Nat. Rev. Mater.,vol. 1, no. 6, p. 16023, 2016].

Sulfur containing compounds are found in most crude oil and otherhydrocarbon fuels such as coal and natural gas as impurities. Thecombustion of fuels containing sulfur species, especially crude oilfractions such as gasoline, diesel, and jet fuels, often leads toemission of SO₂ gas and fine particles into the environment [S. Ma, L.Gao, J. Ma, X. Jin, J. Yao, and Y. Zhao, “Advances on simultaneousdesulfurization and denitrification using activated carbon irradiated bymicrowaves,” Environ. Technol., vol. 33, no. 11, pp. 1225-1230, 2012].These emissions have deleterious impacts on the environment withconsequences for human health and property. As the demand for cleanerfuels increases, desulfurization is a significant priority for improvingcrude oil refining processes. The complete desulfurization of fuels islikely inevitable as stringent regulations are enforced around the worldin response to environmental concerns. For instance, US EnvironmentalProtection Agency (EPA) has limited the allowable sulfur concentrationsto 30 ppmw and 15 ppmw for gasoline and highway diesel, respectively [C.Song, “An overview of new approaches to deep desulfurization forultra-clean gasoline, diesel fuel and jet fuel,” Catal. Today, vol. 86,no. 1-4, pp. 211-263, 2003].

Although hydrodesulfurization (HDS) ensures an efficient removal oflight sulfur species such as mercaptans, sulfides, and disulfides, someorganosulfur compounds such as thiophenes and derivatives remain quitestable under conventional HDS conditions. HDS is ineffective for deepdesulfurization because aromatic sulfur compounds such as thiophene,benzothiophene (BT), and 4,6-dimethyldibenzothiophene (DMDBT) remainunaffected under normal operating conditions. Effective removal of thesearomatic sulfur compounds to low levels require more severe conditionsand sophisticated infrastructures [A. H. M. S. Hussain and B. J.Tatarchuk, “Adsorptive desulfurization of jet and diesel fuels usingAg/TiO_(x)—Al₂O₃ and Ag/TiO_(x)—SiO₂ adsorbents,” Fuel, vol. 107, no. 0,pp. 465-473, 2013; S. A. Ganiyu, S. A. Ali, and K. Alhooshani,“Simultaneous HDS of DBT and 4,6-DMDBT over single-pot Ti-SBA-15-NiMocatalysts: influence of Si/Ti ratio on the structural properties,dispersion and catalytic activity,” RSC Adv., vol. 7, no. 35, pp.21943-21952, 2017; S. Nair and B. J. Tatarchuk, “Supported silveradsorbents for selective removal of sulfur species from hydrocarbonfuels,” Fuel, vol. 89, no. 11, pp. 3218-3225, 2010; and R. T. Yang,Fundamentals and applications. 2001, each incorporated herein byreference in their entirety]. Hence, facile alternative desulfurizationmethods under mild operation conditions are continuously beinginvestigated.

Desulfurization is one of the key routine processes carried out in mostcrude oil refineries around the globe. Conventional hydrodesulfurizationtechnology is widely used for desulfurization. The process ofteninvolves utilizing a HDS catalyst at a high temperature (300-450° C.)and under a high H₂ pressure (3-5 MPa) to yield hydrocarbon fuelscontaining lower amounts of sulfur [S. Brunet, D. Mey, G. Pe'rot, C.Bouchy, and F. Diehl, “On the hydrodesulfurization of FCC gasoline: Areview,” Applied Catalysis A: General, vol. 278, no. 2. pp. 143-172,2005, incorporated herein by reference in its entirety]. However,thiophene (TP) and other related organosulfur compounds such asbenzothiophenes (BT), methylbenzothiophenes (MBT), anddimethylbenzothiophenes (DMBT) are common contaminants found in crudeoil. These aromatic contaminants are stable and therefore difficult toremove by conventional means. The conventional HDS technique ensures theremoval of non-aromatic compounds having sulfur species of low molarmass while the remaining refractory contaminants are often concentratedin higher boiling fractions of the crude oil [D. D. Link and P.Zandhuis, “The distribution of sulfur compounds in hydrotreated jetfuels: Implications for obtaining low-sulfur petroleum fractions,” Fuel,vol. 85, no. 4. pp. 451-455, 2006, incorporated herein by reference inits entirety]. Consequently, further desulfurization is required inorder to guarantee safe and efficient utilization of these fuels.

In view of the forgoing, one objective of the present disclosure is toprovide a method of producing a hydrodesulfurization catalyst havingnickel and molybdenum supported by activated carbon. Another objectiveof the present disclosure is to provide a process of desulfurizing ahydrocarbon feedstock catalyzed by the resulting hydrodesulfurizationcatalyst.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to a methodof producing a Ni/Mo hydrodesulfurization catalyst having nickel andmolybdenum disposed on an activated carbon. The method involves thesteps of mixing an activated carbon with a Ni(II) salt and a Mo(VI) saltin a solvent to form a mixture, drying the mixture at a temperature of50-150° C., thereby producing the Ni/Mo hydrodesulfurization catalyst.The Ni/Mo hydrodesulfurization catalyst is mesoporous with a BET surfacearea of 250-500 m²/g, an average pore diameter of 4-10 nm, and a porevolume of 0.2-3 cm³/g.

In one embodiment, the method further involves calcining the Ni/Mohydrodesulfurization catalyst at a temperature of 160-500° C.

In one embodiment, the Ni/Mo hydrodesulfurization catalyst is calcinedat a temperature of 160-200° C.

In one embodiment, the mixture further comprises a chelating agent whichis ethylenediaminetetraacetic acid, citric acid, or both.

In one embodiment, the method further involves subjecting the mixture toultrasonication.

In one embodiment, the method further involves granulating andpyrolyzing waste tires to form the activated carbon.

In one embodiment, the activated carbon has a BET surface area of500-700 m²/g, an average pore diameter of 3-8 nm, and a pore volume of0.25-4 cm³/g.

In one embodiment, the Ni/Mo hydrodesulfurization catalyst has anactivated carbon content in a range of 60-95% by weight relative to atotal weight of the Ni/Mo hydrodesulfurization catalyst.

In one embodiment, the Ni(II) salt is nickel(II) acetate.

In one embodiment, the Mo(VI) salt is ammonium molybdate(VI).

In one embodiment, the Ni/Mo hydrodesulfurization catalyst has a Ni:Momolar ratio in a range of 1:10 to 1:2.

In one embodiment, the Ni/Mo hydrodesulfurization catalyst has a Mocontent in a range of 4-20% by weight relative to a total weight of theNi/Mo hydrodesulfurization catalyst.

According to a second aspect, the present disclosure relates to a methodfor desulfurizing a hydrocarbon feedstock comprising a sulfur-containingcompound. The method involves contacting the hydrocarbon feedstock witha Ni/Mo hydrodesulfurization catalyst in the presence of H₂ gas toconvert at least a portion of the sulfur-containing compound into amixture of H₂S and a desulfurized product, and removing the H₂S from themixture, thereby forming a desulfurized hydrocarbon stream, wherein (i)the Ni/Mo hydrodesulfurization catalyst comprises nickel and molybdenumdisposed on an activated carbon, (ii) the Ni/Mo hydrodesulfurizationcatalyst has an activated carbon content in a range of 60-95% by weight,a Mo content of 4-20% by weight, each relative to a total weight ofNi/Mo hydrodesulfurization catalyst, and a Ni:Mo molar ratio of 1:10 to1:2, and (iii) the Ni/Mo hydrodesulfurization catalyst is mesoporouswith a BET surface area of 250-500 m²/g, an average pore diameter of4-10 nm, and a pore volume of 0.2-3 cm³/g.

In one embodiment, the hydrocarbon feedstock is contacted with the Ni/Mohydrodesulfurization catalyst at a temperature in a range of 150 to 500°C. for 0.1-10 hours.

In one embodiment, a pressure of the H₂ gas is in a range of 2 to 10MPa.

In one embodiment, the sulfur-containing compound is present in thehydrocarbon feedstock at a concentration of 0.01-10% by weight relativeto a total weight of the hydrocarbon feedstock.

In one embodiment, the sulfur-containing compound is at least oneselected from the group consisting of a sulfide, a disulfide, athiophene, a benzothiophene, and a dibenzothiophene.

In one embodiment, the sulfur-containing compound is dibenzothiophene.

In one embodiment, the sulfur content of the desulfurized hydrocarbonstream is 20-99% by weight less than that of the hydrocarbon feedstock.

In one embodiment, the method further involves treating the Ni/Mohydrodesulfurization catalyst with a mixture comprising H₂ gas at atemperature of 250 to 500° C. to form a reduced Ni/Mohydrodesulfurization catalyst, and presulfiding the reduced Ni/Mohydrodesulfurization catalyst with a sulfide-containing solution at atemperature of 250 to 500° C., prior to the contacting.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 represents N₂ adsorption-desorption isotherms of activatedcarbon.

FIG. 2 represents N₂ adsorption-desorption isotherms of TiO₂.

FIG. 3 represents N₂ adsorption-desorption isotherms of activatedcarbon-TiO₂ composite.

FIG. 4 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst.

FIG. 5 represents N₂ adsorption-desorption isotherms of a TiO₂ supportedNi/Mo catalyst.

FIG. 6 represents N₂ adsorption-desorption isotherms of an activatedcarbon-TiO₂ composite supported Ni/Mo catalyst.

FIG. 7 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst calcined at 100° C.

FIG. 8 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst calcined at 200° C.

FIG. 9 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst calcined at 300° C.

FIG. 10 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst calcined at 400° C.

FIG. 11 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst prepared using ultrasonication.

FIG. 12 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst prepared using citric acid.

FIG. 13 represents N₂ adsorption-desorption isotherms of an activatedcarbon supported Ni/Mo catalyst prepared usingethylenediaminetetraacetic acid (EDTA).

FIG. 14 is an overlay of FT-IR spectra of activated carbon supportedNi/Mo catalysts prepared using ultrasonication (NiMo/AC(U-S)), citricacid (NiMo/AC(CA)), and EDTA (NiMo/AC(EDTA)), respectively.

FIG. 15 is an overlay of FT-IR spectra of activated carbon supportedNi/Mo catalysts calcined at 100° C. (NiMo/AC100), 200° C. (NiMo/AC200),300° C. (NiMo/AC300), and 400° C. (NiMo/AC400), respectively.

FIG. 16 is an overlay of X-ray diffraction patterns of activated carbonsupported Ni/Mo catalysts calcined at 100° C. (NiMo/AC100), 200° C.(NiMo/AC200), 300° C. (NiMo/AC300), and 400° C. (NiMo/AC400),respectively.

FIG. 17 is an SEM image of an activated carbon supported Ni/Mo catalyst.

FIG. 18 is a magnified view of the sample in FIG. 17.

FIG. 19 is an energy dispersive X-ray spectroscopy (EDX) spectrum of anactivated carbon supported Ni/Mo catalyst.

FIG. 20 is a bar graph illustrating hydrodesulfurization catalyticactivities of a TiO₂ supported Ni/Mo catalyst, an activated carbonsupported Ni/Mo catalyst, and an activated carbon-TiO₂ compositesupported Ni/Mo catalyst, respectively, at different contact times.

FIG. 21A is a kinetic plot for hydrodesulfurization activity of a TiO₂supported Ni/Mo catalyst.

FIG. 21B is a kinetic plot for hydrodesulfurization activity of anactivated carbon-TiO₂ composite supported Ni/Mo catalyst.

FIG. 21C is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalyst.

FIG. 22 is a bar graph illustrating hydrodesulfurization catalyticactivities of activated carbon supported Ni/Mo catalysts calcined at100° C. (NiMo/AC100), 200° C. (NiMo/AC200), 300° C. (NiMo/AC300), and400° C. (NiMo/AC400), respectively, at different contact times.

FIG. 23A is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalysts calcined at 100° C.

FIG. 23B is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalysts calcined at 200° C.

FIG. 23C is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalysts calcined at 300° C.

FIG. 23D is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalysts calcined at 400° C.

FIG. 24 is a bar graph illustrating hydrodesulfurization catalyticactivities of activated carbon supported Ni/Mo catalysts prepared usingultrasonication (NiMo/AC(U-S)), citric acid (NiMo/AC(CA)), and EDTA(NiMo/AC(EDTA)), respectively, at different contact times.

FIG. 25A is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalysts prepared usingultrasonication.

FIG. 25B is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalysts prepared using citric acid.

FIG. 25C is a kinetic plot for hydrodesulfurization activity of anactivated carbon supported Ni/Mo catalysts prepared using EDTA.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the disclosure are shown.

As used herein, the words “a” and “an” and the like carry the meaning of“one or more”. Within the description of this disclosure, where anumerical limit or range is stated, the endpoints are included unlessstated otherwise. Also, all values and subranges within a numericallimit or range are specifically included as if explicitly written out.

The term “microporous” refers to a surface having an average porediameter of less than 2 nm, while the term “mesoporous” refers to asurface having an average pore diameter of 2-50 nm.

As used herein, “compound” is intended to refer to a chemical entity,whether as a solid, liquid, or gas, and whether in a crude mixture orisolated and purified.

The present disclosure includes all hydration states of a given salt orformula, unless otherwise noted. For example, nickel(II) acetateincludes anhydrous Ni(OCOCH₃)₂, tetrahydrate Ni(OCOCH₃)₂.4H₂O, and anyother hydrated forms or mixtures. Ammonium heptamolybdate(VI) includesanhydrous (NH₄)₆Mo₇O₂₄, and hydrated forms such as ammoniumheptamolybdate tetrahydrate (NH₄)₆Mo₇O₂₄.4H₂O.

The present disclosure is intended to include all isotopes of atomsoccurring in the present compounds. Isotopes include those atoms havingthe same atomic number but different mass numbers. By way of generalexample, and without limitation, isotopes of hydrogen include deuteriumand tritium, isotopes of carbon include ¹³C and ¹⁴C, isotopes of oxygeninclude ¹⁶O, ¹⁷O and ¹⁸O isotopes of nickel include ⁵⁸Ni, ⁶⁰⁻⁶²Ni, and⁶⁴Ni, and isotopes of molybdenum include ⁹²Mo, ⁹⁴⁻⁹⁸Mo, and ¹⁰⁰Mo.Isotopically labeled compounds of the disclosure can generally beprepared by conventional techniques known to those skilled in the art orby processes and methods analogous to those described herein, using anappropriate isotopically labeled reagent in place of the non-labeledreagent otherwise employed.

A first aspect of the present disclosure relates to a method of making aNi/Mo hydrodesulfurization catalyst having nickel and molybdenumdisposed on an activated carbon. The method involves the steps of mixingan activated carbon with a Ni(II) salt and a Mo(VI) salt in a solvent toform a mixture, and drying the mixture thereby producing the Ni/Mohydrodesulfurization catalyst. The present method may further involvecalcining the Ni/Mo hydrodesulfurization catalyst. This method may beconsidered a wetness impregnation technique, wherein a catalyst supportmaterial (e.g. activated carbon) is contacted with a solution of desiredmetal salts (e.g. Ni(II) and Mo(VI) salts).

As used herein, a catalyst support material refers to a material,usually a solid with a high surface area, to which a catalyst isaffixed. The reactivity of heterogeneous catalyst and nanomaterial basedcatalysts occurs at the surface atoms. Thus, great effort is made hereinto maximize the surface of a catalyst by distributing it over thesupport. The support may be inert or participate in the catalyticreactions. The support materials used in catalyst preparation play arole in determining the physical characteristics and performance of thecatalysts. In a preferred embodiment, an activated carbon serves as acatalyst support material in the presently disclosed Ni/Mohydrodesulfurization catalyst. The activated carbon may be in the formof powdered activated carbon, granular activated carbon, extrudedactivated carbon, bead activated carbon, impregnated carbon, polymercoated carbon but is not limited to such forms of activated carbon. Inat least one embodiment, the activated carbon used herein is in the formof powdered activated carbon.

The Brunauer-Emmet-Teller (BET) theory (S. Brunauer, P. H. Emmett, E.Teller, J. Am. Chem. Soc. 1938, 60, 309-319, incorporated herein byreference) aims to explain the physical adsorption of gas molecules on asolid surface and serves as the basis for an important analysistechnique for the measurement of a specific surface area of a material.Specific surface area is a property of solids which is the total surfacearea of a material per unit of mass, solid or bulk volume, or crosssectional area. In most embodiments, pore diameter, pore volume, and BETsurface area are measured by gas adsorption analysis, preferably N₂adsorption analysis (e.g. N₂ adsorption isotherms). In one or moreembodiments, the activated carbon used herein has a BET surface area of500-700 m²/g, preferably 520-680 m²/g, preferably 540-660 m²/g,preferably 560-640 m²/g, preferably 570-620 m²/g, preferably 580-600m²/g, or about 583 m²/g. In at least one embodiment, the activatedcarbon used herein has a BET surface area that is greater than 500 m²/gand less than 1,000 m²/g. In a related embodiment, the activated carbonhas an average pore diameter of 3-8 nm, preferably 3.5-7.5 nm,preferably 4-7 nm, preferably 4.5-6.5 nm, preferably 5-6 nm, or about5.2 nm. In another related embodiment, the activated carbon has a porevolume of 0.25-4 cm³/g, preferably 0.5-3 cm³/g, preferably 0.6-2.5cm³/g, preferably 0.7-2 cm³/g, preferably 0.8-1.5 cm³/g, preferably0.9-1.2 cm³/g, or about 1 cm³/g.

In a preferred embodiment, the activated carbon is produced from wastetires. In one or more embodiments, the activated carbon is produced bygranulating and pyrolyzing waste tires. For example, pieces of wastetires may be collected from a dumping site, cleaned with water, andoptionally ground to granular form. The granules may be dried at atemperature of 80-160° C., 90-140° C., or 100-120° C. to form driedgranules. The dried granules may be subjected to pyrolysis via heatingat a temperature of 200-600° C., 250-550° C., 300-500° C., or 350-450°C. for 30-600 minutes, 60-500 minutes, 90-400 minutes, 120-300 minutes,150-270 minutes, or 180-240 minutes to form carbonized particles. Thepyrolysis may be conducted in inert gas (e.g. nitrogen, argon, helium)within an oven or furnace. Also, in some embodiments, the dried granulesmay not be pyrolyzed in inert gas, but in a vacuum. Further purificationof the carbonized particles may be optionally accomplished via H₂O₂treatment in order to eliminate adhering organic impurities. Thecarbonized particles may be activated by heating at a temperature of350-950° C., 400-900° C., 450-850° C., 500-800° C., 550-750° C., or600-700° C. for 1-8 hours, 2-7 hours, 3-6 hours, or about 5 hours toform the activated carbon. The activation may be performed within asteam-enriched muffle furnace or an oven. In certain embodiments, thecarbonized particles may not be activated via heating in steam, but inair, or oxygen-enriched air.

Other support materials such as titanium dioxide (TiO₂), an activatedcarbon-TiO₂ composite, an alumina, a magnesia, a zirconia, a chromia, azinc oxide, a thoria, a boria, a silica, a silica-alumina, asilica-magnesia, a chromia-alumina, an alumina-boria, a silica-zirconia,and zeolites may be used in addition to or in lieu of the activatedcarbon. In one embodiment, titanium dioxide (Example 3) having a BETsurface area of 200-450 m²/g, 250-400 m²/g, 300-450 m²/g, 325-400 m²/g,or about 350 m²/g and an average pore diameter of 2-5 nm, 2.5-4.5 nm, or3-4 nm is used as a support material for the preparation of the Ni/Mohydrodesulfurization catalyst. In another embodiment, an activatedcarbon-TiO₂ composite (Example 4) having a BET surface area of 150-400m²/g, 200-350 m²/g, 250-335 m²/g, 275-320 m²/g, or about 310 m²/g and anaverage pore diameter of 3-9 nm, 3.5-8 nm, 4-7 nm, 4.5-6 nm, or about5.6 nm is used as a support material for the preparation of the Ni/Mohydrodesulfurization catalyst. However, in at least one embodiment, thesupport material for the preparation of the Ni/Mo hydrodesulfurizationcatalyst disclosed herein consists essentially of the aforementionedactivated carbon and is devoid of titanium dioxide and activatedcarbon-TiO₂ composite.

Exemplary suitable Ni(II) salts include, but are not limited to,nickel(II) acetate, nickel(II) acetate tetrahydrate, nickel(II)acetylacetonate, nickel(II) hexafluoroacetylacetonate, nickel(II)octanoate, ammonium nickel(II) sulfate, nickel(II) chloride, nickel(II)bromide, nickel(II) fluoride, nickel(II) iodide, nickel(II) carbonate,nickel(II) hydroxide, nickel(II) nitrate, nickel(II) perchlorate,nickel(II) sulfate, nickel(II) sulfamate, and mixtures thereof. Incertain embodiments, a nickel salt having a different oxidation state,such as +1, +3, +4, may be used in addition to or in lieu of the Ni(II)salt. In a preferred embodiment, the Ni(II) salt used herein isnickel(II) acetate.

Exemplary suitable Mo(VI) salts include, but are not limited to,ammonium heptamolybdate(VI), ammonium heptamolybdate(VI) tetrahydrate,ammonium molybdate(VI), ammonium phosphomolybdate, ammoniumtetrathiomolybdate, sodium molybdate(VI), lithium molybdate(VI),molybdenum(VI) dichloride dioxide, and mixtures thereof. In certainembodiments, a molybdenum salt having a different oxidation state, suchas +2 (e.g. molybdenum(I) carboxylates), +3 (e.g. molybdenum(III)chloride), +4 (e.g. molybdenum(IV) carbonate), and +5 (e.g.molybdenum(V) chloride), may be used in addition to or in lieu of theMo(VI) salt. Alternatively, a molybdenum acid, a molybdenum base may beused in addition to or in lieu of the Mo(VI) salt. In a preferredembodiment, the Mo(VI) salt used herein is ammonium heptamolybdate(VI).

The method of making the Ni/Mo hydrodesulfurization catalyst involvesmixing the activated carbon with the Ni(II) salt and the Mo(VI) salt ina solvent to form a mixture. In a preferred embodiment, the solventcomprises water. The water may be tap water, distilled water,bidistilled water, deionized water, deionized distilled water, reverseosmosis water, and/or some other water. In one embodiment, the water isbidistilled to eliminate trace metals. Preferably the water is distilledwater. In certain embodiments, other solvents including, but not limitedto, alcohols (e.g. methanol, ethanol, n-propanol, i-propanol,n-butanol), and acetone may be used in addition to or in lieu of water.

In one or more embodiments, the mixture further comprises a chelatingagent. Exemplary chelating agents that may be used during the mixingstep include, but are not limited to, ethylenediaminetetraacetic acid(EDTA), citric acid, N-hydroxy ethylenediaminetetraacetic acid,diammonium ethylenediaminetetraacetic acid, as well as oxalic acid,malic acid, sebacic acid, tartaric acid, glucose, amino acids such asglutamine and histidine, other triprotic acids such as isocitric acid,aconitic acid, nitriloacetic acid, and propane-1,2,3-tricarboxylic acid,other tetraprotic acids such as cyclohexanediaminetetraacetic acid, andethyleneglycol-bis-(beta-aminoethylether)-N,N′-tetraacetic acid,diethylenetriaminepentaacetic acid, urea, thiourea,tris(2-aminoethyl)amine, triethylenetetraamine, tetraethylenepentaamine,and derivatives thereof. In a preferred embodiment, the chelating agentused herein is ethylenediaminetetraacetic acid, citric acid, or both. Ina most preferred embodiment, ethylenediaminetetraacetic acid is used inthe mixture as a chelating agent.

Prior to the mixing step, the aforementioned reagents (i.e. Ni(II) andMo(VI) salts, and optionally the chelating agent) may be dissolved inthe solvent separately to form respective solutions, which are thenmixed with the activated carbon to form the mixture. In an alternativeembodiment, the metal salts (i.e. Ni(II) and Mo(VI) salts) are dissolvedin the solvent to form a first mixture, and a solution of the chelatingagent is mixed with the first mixture and the activated carbon to formthe mixture. The mixing may occur via stirring, shaking, swirling,sonicating, blending, or by otherwise agitating the mixture. In oneembodiment, the mixture is stirred by a magnetic stirrer or an overheadstirrer. In another embodiment, the mixture is left to stand (i.e. notstirred). Preferably, the mixture is subjected to ultrasonication. Theultrasonication may be performed using an ultrasonic bath or anultrasonic probe. In one embodiment, the mixture is ultrasonicated at afrequency of 20-100 kHz, preferably 30-80 kHz, preferably 40-50 kHz fora time period ranging from 0.1-6 hours, 0.25-4 hours, 0.5-3 hours, or1-2 hours.

In a preferred embodiment, an atomic ratio of the nickel to themolybdenum in the aforementioned mixture is maintained in a range of 1:3to 1:5, 1:4 to 2:9, or about 0.23:1. In a related embodiment, a molarratio of the Ni(II) salt to the Mo(VI) salt is in a range of 1:5 to 2:1,2:9 to 3:2, 1:4 to 1:1, or 1:3 to 1:2. However, in certain embodiments,the molar ratio of the nickel(II) salt to the Mo(VI) salt is less than1:5 or greater than 2:1, depending on the chemical formula of the salts.For example, a molar ratio of the Ni(II) salt Ni(OCOCH₃)₂ to the Mo(VI)salt (NH₄)₆Mo₇O₂₄ may be about 1.38:1 for the preparation of a mixturecomprising nickel and molybdenum at an atomic ration of 0.23:1. And amolar ratio of the Ni(II) salt Ni(OCOCH₃)₂ to the Mo(VI) salt (NH₄)₂MoO₄may be about 0.23:1 for the preparation of a mixture comprising nickeland molybdenum at an atomic ration of 0.23:1. In one embodiment, theMo(VI) salt may present at a concentration of 5-25 wt %, 8-20 wt %,10-18 wt %, or 12-15 wt % relative to a total weight of the activatedcarbon.

The method also involves the step of drying the mixture to form theNi/Mo hydrodesulfurization catalyst. In a preferred embodiment, themixture is dried at a first temperature of 40-95° C., preferably 50-90°C., preferably 60-85° C., preferably 70-80° C. for 0.1-6 hours, 0.25-5hours, 0.5-4 hour, or 1-2 hours, and subsequently at a secondtemperature of 100-150° C., preferably 105-140° C., preferably 108-120°C., or about 110° C. for 1-48 hours, 2-36 hours, 3-24 hours, 4-12 hours,or 6-8 hours. A Ni/Mo hydrodesulfurization catalyst may be formed duringthe drying processes and be separated (e.g. filtered off, centrifuged)from the aforementioned mixture. Alternatively, the mixture may beheated in a single stage. For example, the mixture may be dried at atemperature of 40-150° C., preferably 50-140° C., preferably 60-130° C.,preferably 70-120° C., preferably 80-110° C. for 1-48 hours, 2-24 hours,4-12 hours, or 6-8 hours. An external heat source, such as a water bathor an oil bath, an oven, or a heating mantle, may be employed to dry themixture. Alternatively, the mixture may be air dried or dried in anoven.

The present method may optionally further involve the step of calcining(i.e. heating) the Ni/Mo hydrodesulfurization catalyst at a temperatureof 160-500° C., 180-450° C., 200-400° C., 250-350° C., or 275-325° C.for 1-8 hours, 2-6 hours, 2.5-4 hours, or about 3 hours. In a preferredembodiment, when the calcination step is performed, the Ni/Mohydrodesulfurization catalyst is calcined at a temperature below 250°C., preferably at a temperature of 160-220° C., more preferably at atemperature of about 200° C. Calcination can be carried out in airwithin shaft furnaces, rotary kilns, multiple hearth furnaces, and/orfluidized bed reactors. Also, in some embodiments, the dried mass maynot be calcined via heating in air, but in oxygen-enriched air, an inertgas, or a vacuum. In at least one embodiment, the Ni/Mohydrodesulfurization catalyst disclosed herein is prepared without acalcination step and used directly after the drying.

In one or more embodiments, the Ni/Mo hydrodesulfurization catalystprepared by the method of the first aspect has nickel and molybdenumdisposed on the activated carbon. As used herein, “disposed on”describes catalytic materials being deposited on or impregnated in asupport material such that the support material is completely orpartially filled throughout, saturated, permeated, and/or infused withthe catalytic materials. The catalytic materials (i.e. nickel andmolybdenum) may be affixed to the activated carbon in any reasonablemanner, such as physisorption, chemisorption, or mixtures thereof. In arelated embodiment, the Ni/Mo hydrodesulfurization catalyst of thepresent disclosure may have both nickel and molybdenum decorated on thesurface of the activated carbon. In another related embodiment, theNi/Mo hydrodesulfurization catalyst may have both nickel and molybdenumdisposed on the surface and impregnated in the activated carbon. Inpreferred embodiments, the nickel and molybdenum are homogeneouslydispersed in the activated carbon.

In one embodiment, greater than 10% of the surface area (i.e. surfaceand pore spaces) of the activated carbon is covered by the nickel andmolybdenum, preferably greater than 15%, preferably greater than 20%,preferably greater than 25%, preferably greater than 30%, preferablygreater than 35%, preferably greater than 40%, preferably greater than45%, preferably greater than 50%, preferably greater than 55%,preferably greater than 60%, preferably greater than 65%, preferablygreater than 70%, preferably greater than 75%, preferably greater than80%, preferably greater than 85%, preferably greater than 90%,preferably greater than 95%, preferably greater than 96%, preferablygreater than 97%, preferably greater than 98%, preferably greater than99% of the activated carbon is covered by the nickel and molybdenum.

Preferably, the Ni/Mo hydrodesulfurization catalyst has an activatedcarbon content in a range of 60-95%, preferably 65-90%, preferably70-88%, preferably 75-85%, preferably 78-82% by weight relative to atotal weight of the Ni/Mo hydrodesulfurization catalyst. However, incertain embodiments, the activated carbon may present in the Ni/Mohydrodesulfurization catalyst at a concentration that is less than 60%or greater than 95% by weight relative to a total weight of the Ni/Mohydrodesulfurization catalyst.

In one or more embodiments, the Ni/Mo hydrodesulfurization catalystdisclosed herein has a Mo content in a range of 4-20%, preferably4.5-18%, preferably 5-15%, preferably 5.5-12%, preferably 6-10 wt %,preferably 6.5-9%, preferably 7-8%, or about 7.5% by weight relative toa total weight of the Ni/Mo hydrodesulfurization catalyst. However, incertain embodiments, the Ni/Mo hydrodesulfurization catalyst has a Mocontent that is less than 4% or greater than 20% by weight relative to atotal weight of the Ni/Mo hydrodesulfurization catalyst. Preferably,molybdenum is present in the Ni/Mo hydrodesulfurization catalyst inoxide forms (e.g. MoO₂, MoO₃). However, in certain embodiments,molybdenum may be present in other species such as metallic molybdenumand sulfide forms in the Ni/Mo hydrodesulfurization catalyst in additionto, or in lieu of molybdenum oxides.

In a preferred embodiment, the Ni/Mo hydrodesulfurization catalyst has aNi:Mo molar ratio ranging from 1:10 to 1:2, from 1:9 to 2:3, from 1:8 to1:1, from 1:7 to 2:3, from 1:6 to 1:2, from 1:5 to 1:3, or from 1:4 to2:7. However, in certain embodiments, the Ni/Mo hydrodesulfurizationcatalyst has a Ni:Mo molar ratio that is less than 1:10 or greater than1:2. Preferably, nickel is present in the Ni/Mo hydrodesulfurizationcatalyst in oxide forms (e.g. NiO, Ni₂O₃). However, in certainembodiments, nickel may be present in other species such as metallicnickel and sulfide forms in the Ni/Mo hydrodesulfurization catalyst inaddition to, or in lieu of nickel oxides.

The Ni/Mo hydrodesulfurization catalyst disclosed herein may be in theform of particles having spherical or substantially spherical shape(e.g., oval or oblong shape). In some embodiments, the Ni/Mohydrodesulfurization catalyst is in the form of at least one shape suchas a sphere, a rod, a cylinder, a rectangle, a triangle, a pentagon, ahexagon, a prism, a disk, a platelet, a flake, a cube, a cuboid, and anurchin (e.g., a globular particle possessing a spiky uneven surface). Inone or more embodiments, the Ni/Mo hydrodesulfurization catalyst has aBET surface area of 250-500 m²/g, 275-475 m²/g, 300-450 m²/g, 325-425m²/g, 350-400 m²/g, or 365-380 m²/g. Preferably, the Ni/Mohydrodesulfurization catalyst is mesoporous. In a related embodiment,the Ni/Mo hydrodesulfurization catalyst has an average pore diameter of4-10 nm, 4.5-9.5 nm, 5-9 nm, 5.5-8.5 nm, 6-8 nm, or 6.5-7 nm. In anotherrelated embodiment, the Ni/Mo hydrodesulfurization catalyst has a porevolume of 0.2-3 cm³/g, 0.3-2.8 cm³/g, 0.4-2.5 cm³/g, 0.5-2.2 cm³/g,0.6-2 cm³/g, 0.7-1.8 cm³/g, 0.8-1.5 cm³/g, or 0.9-1.2 cm³/g.

According to a second aspect, the present disclosure relates to a methodfor desulfurizing a hydrocarbon feedstock comprising a sulfur-containingcompound. The method involves contacting the hydrocarbon feedstock witha Ni/Mo hydrodesulfurization catalyst that has nickel and molybdenumdisposed on an activated carbon, in the presence of H₂ gas to convert atleast a portion of the sulfur-containing compound into a mixture of H₂Sand a desulfurized product, and removing the H₂S from the mixture,thereby forming a desulfurized hydrocarbon stream. The Ni/Mohydrodesulfurization catalyst used herein may have similar properties asdescribed for that in the first aspect, such as composition, surfacearea, pore size, pore volume, and/or some other property. The Ni/Mohydrodesulfurization catalyst with similar properties may be formed byfollowing the aforementioned reaction conditions, such as reagents,solvent, reaction time, and/or temperature.

Preferably, the Ni/Mo hydrodesulfurization catalyst used herein has anactivated carbon content in a range of 60-95%, preferably 65-90%,preferably 70-88%, preferably 75-85%, preferably 78-82% by weightrelative to a total weight of the Ni/Mo hydrodesulfurization catalyst.Preferably, the Ni/Mo hydrodesulfurization catalyst used herein has a Mocontent in a range of 4-20%, preferably 4.5-18%, preferably 5-15%,preferably 5.5-12%, preferably 6-10 wt %, preferably 6.5-9%, preferably7-8%, or about 7.5% by weight relative to a total weight of the Ni/Mohydrodesulfurization catalyst. Preferably, the Ni/Mohydrodesulfurization catalyst has a Ni:Mo molar ratio ranging from 1:10to 1:2, from 1:9 to 2:3, from 1:8 to 1:1, from 1:7 to 2:3, from 1:6 to1:2, from 1:5 to 1:3, or from 1:4 to 2:7. Preferably, the Ni/Mohydrodesulfurization catalyst used herein has a BET surface area of250-500 m²/g, 275-475 m²/g, 300-450 m²/g, 325-425 m²/g, 350-400 m²/g, or365-380 m²/g. Preferably, the Ni/Mo hydrodesulfurization catalyst ismesoporous and has an average pore diameter of 4-10 nm, 4.5-9.5 nm, 5-9nm, 5.5-8.5 nm, 6-8 nm, or 6.5-7 nm. Preferably, the Ni/Mohydrodesulfurization catalyst used herein has a pore volume of 0.2-3cm³/g, 0.3-2.8 cm³/g, 0.4-2.5 cm³/g, 0.5-2.2 cm³/g, 0.6-2 cm³/g, 0.7-1.8cm³/g, 0.8-1.5 cm³/g, or 0.9-1.2 cm³/g.

The hydrocarbon feedstock may be delivered from a hydrocarbon reservoiror directly from an offshore or an onshore well. For example, thehydrocarbon feedstock may be a crude oil that is produced from an oilwell, particularly from a sour gas oil well. Alternatively, thehydrocarbon feedstock may be a gaseous stream that is supplied directlyfrom an offshore or an onshore well, or a sulfur-containing liquid orgaseous stream, e.g. gaseous ethane, liquid gasoline, liquid naphtha,etc. in a refinery or a petrochemical plant that needs to bedesulfurized.

The hydrocarbon feedstock including a sulfur-containing compound mayalso include various hydrocarbon compounds such as C₁₋₅₀ hydrocarboncompounds, preferably C₂₋₃₀ hydrocarbon compounds, preferably C₃₋₂₀hydrocarbon compounds, depending on the origin of the hydrocarbonfeedstock. In one embodiment, the hydrocarbon feedstock includes C₁₋₂₀normal paraffins, e.g. C₁₋₂₀ alkanes, C₁₋₂₀ isoparaffins, C₁₋₂₀cycloparaffins (i.e. naphthenes) or C₁₋₂₀ cycloparaffins having sidechain alkyl groups, C₁₋₂₀ aromatics or C₁₋₂₀ aromatics with side chainalkyl groups.

Exemplary sulfur-containing compounds include, but are not limited to,H₂S, elemental sulfur, carbon disulfide, dimethyl disulfide, ethyldisulfide, propyl disulfide, isopropyl disulfide, butyl disulfide,tertiary butyl disulfide, thianaphthene, thiophene, secondary dibutyldisulfide, thiols, methyl mercaptan, phenyl mercaptan, cyclohexythiol,methyl sulfide, ethyl sulfide, propyl sulfide, isopropyl sulfide, butylsulfide, secondary dibutyl sulfide, tertiary butyl sulfide,benzothiophene, dibenzothiophene, alkyl benzothiophene, alkyldibenzothiophene, thiocyclohexane, and/or any combination thereof.

In one or more embodiments, the sulfur-containing compound is at leastone selected from the group consisting of a sulfide, a disulfide, athiophene, a benzothiophene, and a dibenzothiophene. In a preferredembodiment, the sulfur-containing compound is a dibenzothiophene.Exemplary dibenzothiophenes include, but are not limited to,dibenzothiophene, 4-methyldibenzothiophene,4,6-dimethyldibenzothiophene, and 4,6-diethyldibenzothiophene.

In one or more embodiments, the sulfur-containing compound may bepresent in the hydrocarbon feedstock at a concentration of 0.01-10%,preferably at least 0.05%, at least 0.1%, at least 1%, at least 3%, atleast 5%, at least 6%, at least 7%, at least 8%, at least 9% by weight,and no more than 10% by weight, relative to a total weight of thehydrocarbon feedstock. In a related embodiment, a concentration of thesulfur-containing compound in the hydrocarbon feedstock is no more than50,000 ppm, preferably no more than 20,000 ppm, preferably no more than10,000 ppm, preferably no more than 5,000 ppm, preferably no more than4,000 ppm, preferably no more than 2,000 ppm. In an alternativeembodiment, a concentration of sulfur-containing compound in thehydrocarbon feedstock is in the range of 100 to 10,000 ppm, preferably250 to 7,500 ppm, preferably 500 to 5,000 ppm, preferably 750 to 2,500ppm, preferably 1,000 to 2,000 ppm.

The hydrocarbon feedstock may be contacted with the Ni/Mohydrodesulfurization catalyst in the presence of H₂ gas under favorablereaction conditions to convert at least a portion of thesulfur-containing compound into a mixture of H₂S and a desulfurizedproduct. In a preferred embodiment, the hydrocarbon feedstock iscontacted with the Ni/Mo hydrodesulfurization catalyst at a temperaturein a range of 150 to 500° C., preferably 200-450° C., preferably300-400° C., or about 350° C. for 0.1-10 hours, 0.5-8 hours, 1-6 hours,2-5 hours, or 3-4 hours. In one or more embodiments, a pressure of theH₂ gas is in a range of 2 to 10 MPa, preferably 3 to 9 MPa, preferably3.5-8 MPa, preferably 4-7 MPa, preferably 4.5-6 MPa, or about 5 MPa. Avolumetric flow ratio of the H₂ gas to the hydrocarbon feedstock mayvary depending on the type of sulfur-containing compound present in thehydrocarbon feedstock. In some embodiments, the volumetric flow ratio ofthe H₂ gas to the hydrocarbon feedstock is in a range of 100:1 to 1:100,preferably 80:1 to 1:80, preferably 50:1 to 1:50, preferably 40:1 to1:40, preferably 30:1 to 1:30.

The hydrocarbon feedstock may be in a liquid state or a gaseous state.In view of that, contacting the hydrocarbon feedstock with the Ni/Mohydrodesulfurization catalyst may be different, depending on the stateof the hydrocarbon feedstock, i.e. the liquid state or the gaseousstate. In one embodiment, the hydrocarbon feedstock is in a liquid stateor in a gaseous state and the hydrocarbon feedstock is passed throughthe Ni/Mo hydrodesulfurization catalyst via a fixed-bed or afluidized-bed reactor. In another embodiment, the hydrocarbon feedstockis in a gaseous state and the hydrocarbon feedstock is passed over theNi/Mo hydrodesulfurization catalyst, or may stay stagnant over the Ni/Mohydrodesulfurization catalyst, i.e. as an atmosphere to the catalyst.Yet in another embodiment, the hydrocarbon feedstock is in a liquidstate and the hydrocarbon feedstock is mixed with the Ni/Mohydrodesulfurization catalyst to form a heterogeneous mixture in a batchreactor equipped with a rotary agitator.

In one embodiment, the contacting converts by weight 20-99.8%,preferably at least 25%, preferably at least 30%, preferably at least40%, preferably at least 50%, preferably at least 60%, preferably atleast 70%, preferably at least 80%, preferably at least 90%, preferablyat least 95%, preferably at least 99% of the sulfur-containing compoundpresent in the hydrocarbon feedstock into a mixture of H₂S and adesulfurized product. The method disclosed herein may include removingthe H₂S from the mixture in the presence of a nitrogen stream to form adesulfurized hydrocarbon stream. “Removing”, as used herein, may referto any process of separating, at least one component from a mixture.Exemplary removing processes include, but are not limited to,distillation, absorption, adsorption, solvent extraction, stripping, andfiltration and are well known to those skilled in the art. The removedH₂S may be collected and further supplied to a sulfur manufacturingplant to produce sulfur-containing products.

In one or more embodiments, the sulfur content of the desulfurizedhydrocarbon stream is by weight 20-99.8%, preferably at least 25%,preferably at least 30%, preferably at least 40%, preferably at least50%, preferably at least 60%, preferably at least 70%, preferably atleast 80%, preferably at least 90%, preferably at least 95%, preferablyat least 99% less than that of the hydrocarbon feedstock prior to thecontacting.

As used herein, the term “k_(HDS)” refers to a rate constant ofdesulfurization reactions catalyzed by the Ni/Mo hydrodesulfurizationcatalyst.

Traditionally, metal doping is often used to improve performance ofhydrodesulfurization catalysts. However, the presently disclosed Ni/Mohydrodesulfurization catalyst that is supported by the aforementionedactivated carbon demonstrates greater catalytic activity than a Ni/Mohydrodesulfurization catalyst that is supported by a metal-containingcatalyst support (e.g. TiO₂, activated carbon-TiO₂ composite). In oneembodiment, the rate constant of desulfurization reactions catalyzed bythe Ni/Mo hydrodesulfurization catalyst that is supported by theaforementioned activated carbon is at least 15% greater than that of aNi/Mo hydrodesulfurization catalyst that is supported by ametal-containing catalyst support (e.g. TiO₂, activated carbon-TiO₂composite), preferably at least 20%, preferably at least 25%, preferablyat least 30%, preferably at least 35%, preferably at least 40%,preferably at least 45%, preferably at least 50%, preferably at least55%, preferably at least 60% greater than that of a Ni/Mohydrodesulfurization catalyst that is supported by a metal-containingcatalyst support (e.g. TiO₂, activated carbon-TiO₂ composite) (see Table7).

It is worth noting that the presently disclosed Ni/Mohydrodesulfurization catalysts that are not calcined or calcined at alow temperature (e.g. 200° C.) demonstrate greater catalytic activitythan those calcined at a high temperature (e.g. 300° C., 400° C.). Inone embodiment, the rate constant of desulfurization reactions catalyzedby the Ni/Mo hydrodesulfurization catalysts that are not calcined orcalcined at a low temperature (e.g. 200° C.) is at least 50% greaterthan those calcined at a high temperature (e.g. 300° C., 400° C.),preferably at least 52%, preferably at least 54%, preferably at least56%, preferably at least 58%, preferably at least 60%, preferably atleast 62%, preferably at least 64%, preferably at least 66%, preferablyat least 68% greater than those calcined at a high temperature (e.g.300° C., 400° C.) (see Table 9).

In another embodiment, the rate constant of desulfurization reactionscatalyzed by the Ni/Mo hydrodesulfurization catalyst that is preparedusing a complexing agent (e.g. EDTA, citric acid) is at least 12%greater than that of a Ni/Mo hydrodesulfurization catalyst not producedusing the complexing agent, preferably at least 15%, preferably at least20%, preferably at least 25%, preferably at least 30%, preferably atleast 35%, preferably at least 40%, preferably at least 45%, preferablyat least 50%, preferably at least 55%, preferably at least 60%,preferably at least 65% greater than that of a Ni/Mohydrodesulfurization catalyst not produced using the complexing agent(see Tables 9 and 11).

Prior to contacting with the hydrocarbon feedstock, the Ni/Mohydrodesulfurization catalyst may be treated with a mixture comprisingH₂ gas. Preferably, the Ni/Mo hydrodesulfurization catalyst is treatedwith the mixture comprising H₂ gas at a temperature in a range of 250 to500° C., preferably 300-450° C., preferably 350-425° C., or about 400°C. for 0.5 to 6 hours, preferably 1-4 hours, preferably 1.5-3 hours, orabout 2 hours to form a reduced Ni/Mo hydrodesulfurization catalyst. Inone embodiment, the mixture is passed through the Ni/Mohydrodesulfurization catalyst, wherein the mixture contains 2 to 10 vol%, preferably 4 to 6 vol %, or about 5 vol % of H₂ gas diluted innitrogen, helium, and/or argon, with the volume percent being relativeto a total volume of the mixture.

The reduced Ni/Mo hydrodesulfurization catalyst may be presulfided priorto being contacted with the hydrocarbon feedstock. Preferably, thereduced Ni/Mo hydrodesulfurization is presulfided with asulfide-containing solution at a temperature in a range of 250 to 450°C., preferably 300 to 400° C., or about 350° C. The sulfide-containingsolution used herein may include carbon disulfide (CS₂), and may furtherinclude dimethyl disulfide, ethylene sulfide, trimethylene sulfide,propylene sulfide, and bis(methylthio)methane. This step may convertactive catalyst materials in oxide form to their corresponding sulfideform, which may be catalytically more active than the oxide form.

The examples below are intended to further illustrate protocols forpreparing, characterizing the Ni/Mo hydrodesulfurization catalyst, anduses thereof, and are not intended to limit the scope of the claims.

Example 1 Materials

Activated carbon (AC) derived from waste tires, ammonium molybdate[(NH₄)₆Mo₇O₂₄.4H₂O], nickel acetate [Ni(C₂H₃O₂)₂.4 H₂O], cobalt nitrate[Co(NO₃)₂.6 H₂O], decahydronaphthalene (decalin) [C₁₀H₁₈],dibenzothiophene (DBT) [C₁₂H₈S], citric acid (CA) [C₆H₁₀O₇],ethylenediaminetetracetic acid (EDTA) [C₁₀H₁₆N₂O₈], and deionized water[H₂O].

The ammonium molybdate, nickel acetate, and cobalt nitrate were A.C.Scertified analytical grades from Fisher Scientific Company, USA. Decalin(99%) and DBT (98%) were obtained from Sigma Aldrich. All the reagentswere used as purchased from the manufacturers without any form ofpretreatment or modification.

Example 2 Preparation of Support Materials: Preparation of ActivatedCarbon Support

Activated carbon support was prepared from waste rubber tires accordingto the detailed procedure described in a previous report [V. K. Gupta,I. Ali, T. A. Saleh, M. N. Siddiqui, and S. Agarwal, “Chromium removalfrom water by activated carbon developed from waste rubber tires,”Environ. Sci. Pollut. Res., vol. 20, no. 3, pp. 1261-1268, 2013,incorporated herein by reference in its entirety].

Example 3 Preparation of Support Materials: Preparation of TiO₂ Support

TiO₂ was prepared through a modified sol-gel and hydrothermal synthesisroute reported in the literature. A dilute aqueous solution of TiCl₄ wasprepared by adding 20 mL of TiCl₄ to 40 mL ethanol kept in an ice bath.The calculated amount of deionized water was added to the solution toform a 2 molar stock of TiCl₄. Appropriate amounts of the solution wereadded to a round bottom flask, which was then placed in an oil bathsitting on a hot plate/magnetic stirrer. Drops of diluted aqueousammonia were added to the solutions until a gel was formed whilestirring at a solution was stirred at 350 rpm and the temperature wasset at 80° C. The gel was allowed to age for 24 h before filtration andwashing with distilled water to remove the excess base. The material wasfiltered and allowed to dry in an oven.

Example 4 Preparation of Support Materials: Preparation of Carbon-TiO₂Composite Support

6 g of activated carbon was added to 80 mL of deionized water andstirred for 1 h. The mixture was transferred to a round bottom flaskcontaining 20 mL of the TiCl₄ prepared previously. Then diluted aqueousammonia was added dropwise to the solutions until a gel was formed whilethe solution was stirred at 350 rpm and the temperature was set at 80°C. The gel was allowed to age for 24 h before filtration and washingwith distilled water to remove the excess base. The material wasfiltered and allowed to dry in an oven.

Example 5

Preparation of HDS Catalysts: NiMo/AC, NiMo/TiO₂, and NiMo/AC-TiO₂

NiMo/AC was prepared through co-impregnation of the activated carbonwith Ni and Mo using aqueous solutions each containing an appropriateamount of the metallic salts. 6 g of the activated carbon was added toaqueous solutions containing calculated amounts of the metal salts andsubjected to continuous stirring for 2 hrs. Nickel acetate and ammoniumheptamolybdate were used as the precursors to prepare a set of solutionscontaining 13 wt % Mo with the atomic ratio of Ni/Mo maintained at 0.23for all samples. Afterwards, stirring was stopped and the solution wasallowed to evaporate at 70° C. and then dried at 120° C. for 24 h. BothNiMo/TiO₂ and NiMo/AC-TiO₂ were prepared in a similar fashion as NiMo/Acusing TiO₂ and AC-TiO₂ as the support, respectively. The dried materialswere subjected to further calcination at 300° C. for 3 hrs and labeledaccordingly.

Example 6 Preparation of HDS Catalysts: Mo/AC, NiMo/AC, and CoMo/AC

Mo/AC was prepared through impregnation of the activated carbon with Mousing an aqueous solution of the salt containing 13 wt % of the metal.NiMo/AC and CoMo/AC were prepared through the co-impregnation of theactivated carbon with Mo and Ni, and Mo and Co, respectively, asindicated by the labels. The atomic ratios of Ni/Mo and Co/Mo, were 0.23for both NiMo/AC and CoMo/AC, while the total metal loading wasmaintained at 13 wt %. at Mo using aqueous solutions containing theappropriate amounts of their metallic salts. In all cases, 6 g of theactivated carbon was added to aqueous solutions containing calculatedamounts of the metal salts which were subjected to continuous stirringfor 2 hrs. Afterwards, the stirring was stopped and the solution wasallowed to evaporate at 70° C. and then dried at 120° C. for 24 h. Someof the dried materials were subjected to further calcination at 300° C.for 3 hrs and were labeled according to the materials' composition.

Example 7 Preparation of HDS Catalysts: NiMo/AC, NiMo/AC 200,NiMo/AC300, and NiMo/AC400

NiMo/AC was prepared through the co-impregnation of activated carbonsupport with Ni and Mo as using aqueous solutions containing theappropriate amounts of the metal salts. 6 g of the activated carbon wasadded to aqueous solutions containing calculated amounts of the metalsalts which were subjected to continuous stirring for 2 hrs prior toevaporation at 70° C. and subsequent drying at 110° C. NiMo/AC 200,NiMo/AC300 and NiMo/AC400 were prepared in a similar way as NiMo/AC butthe catalysts were subjected to calcination for 3 h at differenttemperatures after the drying at 110° C. NiMo/AC 200, NiMo/AC300, andNiMo/AC400 were calcined at 200° C., 300° C., and 400° C., respectively.The catalysts were labeled such that the figures reflect the calcinationtemperature and the composition of each prepared catalysts.

Example 8 Preparation of HDS Catalysts: NiMo/AC, NiMo/AC(US),NiMo/AC(CA), and NiMo/AC(EDTA)

NiMo/AC was prepared through the co-impregnation of activated carbonsupport with Ni and Mo as using aqueous solutions containing theappropriate amounts of their metal salts. 6 g of the activated carbonwas added to aqueous solutions containing calculated amounts of themetal salts which were subjected to continuous stirring for 2 hrs priorto evaporation at 70° C. and subsequent drying at 110° C. As forNiMo/AC(US), 30 min. ultrasonication was used to facilitate thedispersion of the active metals during the impregnation. In the case ofNiMo/AC(CA) and NiMo/AC(EDTA), chelating agents citric acid andethylenediaminetetracetic acid (EDTA), were used respectively tofacilitate the dispersion of the active phase. In all cases, 6 g of thesupport was used and the metal loading was maintained at 13 wt %. Theimpregnation mixture was allowed to evaporate at 70° C. and then driedat 120° C. for 24 h. The dried materials were subjected to calcinationat 300° C. for 3 h and then labeled using the initials of the dispersionmedium.

Example 9 Characterization of Support Materials and Catalysts (i) TGA

Dried catalysts without calcination were used for the TGA analysis andall experiments were conducted using a Mettler-Toledo TGA/SDTA 851^(e),under static air atmosphere and a heating rate of 10° C./min from 40 to1000° C.

(ii) FT-IR

Fourier transform infrared spectroscopy (FT-IR) was used to identifyvarious functional groups present on the bare support and the catalystssupported on the active carbon using a Nicolet 6700 spectrometer (ThermoElectron). Pellets of the samples were made by adding KBr as a binderand the absorption spectra were obtained with 64 scans.

(iii) XRD

Powder X-ray diffraction (XRD) of the passivated sample was performed ona Bruker D8 focus diffractometer, with Cu Kα radiation at 40 kV and 40mA. Powder diffractograms were recorded at a scanning speed of 12° min⁻¹over a 2θ range of 10-80°.

(iv) Textural Properties

N₂ adsorption-desorption isotherms were obtained for the bare activatedcarbon and then the supported catalysts after calcination at 300° C.under N₂ temperature. BET surface areas, pore volumes, and pore sizedistributions were measured under a liquid nitrogen atmosphere (−196°C.) using a micromeritics ASAP 2020 automatic analyzer. All samples weredegassed at 150° C. for 3 h and then allowed to cool before theexperiments.

(v) SEM-EDX

Scanning Electron Microscope JEOL-JSM6610LV was used to examine themorphology of the samples using secondary electron (SE) andbackscattered electron (BSE) mode at an accelerating voltage of 20 kV,and the attached energy dispersive X-ray spectrometer (EDS, Oxford Inc.)detector was employed for subsequent elemental composition analysis andelement mapping of the samples.

Example 10 Catalysts Activity Tests

The catalytic activity of the prepared materials towards HDS of DBT wasevaluated in a high-pressure batch reactor (model: Parr 4576B) at 350°C. under 5 MPa of H₂ pressure and a constant 300 rpm stirring. 0.3 g ofeach catalyst was used for reactions conducted using 100 mL of DBT fuelmodel. Decalin (decahydronaphthalene) was used as a solvent for thepreparation of the model fuel containing 1000 ppm S (0.588 g of DBT).The catalytic activity tests lasted 4 h after the reactor temperaturereached the set point of 350° C. and aliquots of the product were takenfrom the reactor at an interval of one hour. Prior to the tests, eachcatalysts was pre-sulfided using a solution containing 2 wt. % CS₂ in aquartz tube at 350° C. for 5 h after reduction with of 5% H₂/He (60mL/min) at 400° C. for 2 h.

Example 11 Textural Properties of Support Materials and Catalysts

Textural properties of the support materials are presented in Table 1.Analysis of the results shows that AC has the largest BET surface areaof 583 m²/g compared to 354 m²/g and 310 m²/g recorded for TiO₂ andAC-TiO₂, respectively. A similar trend is observed for the externalsurface area and micropore area of the three support materials. AlthoughTiO₂ has a larger BET surface area and external surface area thanAC-TiO₂, it is important to note that the micropore area of TiO₂ isexceptionally small when compared to the micropore areas of AC andAC-TiO₂, which is a composite of AC and TiO₂. The observations aboveindicate that AC, TiO₂, and AC-TiO₂ have unique surface and texturalproperties. Moreover, the total pore volumes as well as the average porediameter of the three support materials are different. While the totalpore volumes recorded for AC, TiO₂ and AC-TiO₂ were 0.97, 0.26, and 0.43cm³/g, the average pore diameters were approximately 52, 20, and 55 Å(55.22, 3.0 and 5.5 nm), respectively.

TABLE 1 Textural Properties of Catalysts' Support Materials: AC, TiO₂,and AC-TiO₂ BET External Total pore Average Surface Surface Microporevolume of pore Catalysts' Area Area Area pores diameter supports (m²/g)(m²/g) (m²/g) (cm³/g) (Å) AC 583.3670 350.1640 233.2031 0.979245 52.3220TiO₂ 354.4782 349.9376 4.5405 0.263163 29.6959 AC-TiO₂ 310.5169 219.177491.3395 0.432088 55.6604

The average pore diameters of the three catalysts indicate that all thesupport materials are mesoporous, since the values are all greater than2 nm and less than 50 nm [C. Liang, Z. Li, and S. Dai, “Mesoporouscarbon materials: synthesis and modification.,” Angew. Chem. Int. Ed.Engl., vol. 47, no. 20, pp. 3696-717, 2008; and W. Li, J. Liu, and D.Zhao, “Mesoporous materials for energy conversion and storage devices,”Nat. Rev. Mater., vol. 1, no. 6, p. 16023, 2016, each incorporatedherein by reference in their entirety]. Moreover, N₂adsorption-desorption isotherms of all the prepared support materialsare similar to the type-IV isotherm exhibited by mesoporous materials.The N₂ adsorption-desorption isotherms for AC, TiO₂, and AC-TiO₂ arepresented in FIGS. 1, 2, and 3, respectively. The shapes of isotherm forAC and TiO₂ are similar but there is a slight distortion in the case ofAC-TiO₂, different in the amount of N₂ adsorbed in each case. Theobserved distortion in the shape of AC-TiO₂ N₂ adsorption-desorptionisotherm could be considered as a reflection of the composite nature ofthe support material comprising both AC and TiO₂.

Textural properties of the catalysts supported on AC, TiO₂, and AC-TiO₂are presented in Table 2. Analysis of the results shows that thetextural properties of the support have impact on loading the supportswith equivalent amounts of metal catalyst. A reduction in the BETsurface, external surface area, and micropore area of the supportmaterials can be observed when comparing the values in Table 2 and Table3. For example, the BET surface of AC is reduced from 583 m²/g to 352m²/g upon loading the Ni and Mo metal species onto the support materialto form the corresponding NiMo/AC catalyst. A similar trend of reductionin BET surface area is observed when comparing TiO₂ and AC-TiO₂ tocorresponding catalysts NiMo/TiO₂ and NiMo/AC-TiO₂, respectively. Theobserved reduction in the BET surface area, external surface area,micropore area, and the total pore volume of the of the supportmaterials, when compared to the corresponding HDS catalysts, is anindication of the successful incorporation of the metal catalysts ontothe support materials.

TABLE 2 Textural Properties of Catalysts: NiMo/AC, NiMo/TiO₂, andNiMo/AC-TiO₂ BET External Total pore Average Surface Surface Microporevolume of pore Area Area Area pores diameter Catalysts (m²/g) (m²/g)(m²/g) (cm³/g) (Å) NiMo/AC 352.1114 230.7778 121.3336 0.530329 60.2456NiMo/TiO₂ 225.82 220.98 2.633 0.3218 31.751 NiMo/AC-TiO₂ 220.8506170.6991 50.1515 0.475779 86.1721

Another interesting observation is the change in the average pore sizeof the support materials upon incorporation of the metal catalysts.After the impregnation with Ni and Mo species, average pore diameters ofAC, TiO₂, and AC-TiO₂ increased from initial values of 52 Å (5.2 nm), 30Å (3.0 nm), and 56 Å (5.6 nm) to 60 Å (6.0 nm), 31 Å (3.1 nm), and 86 Å(8.6 nm), respectively. The observed increase in pore diameter could beattributed to the occupation or blocking of some of the micro pores ofthe support materials by the metal nanoparticles, and thus leading to adecrease in the ratio of the micropores relative to the mesopores.Moreover, based on the shapes of the N₂ adsorption-desorption isothermsof the catalyst presented on FIGS. 4, 5, and 6, it is clear thatNiMo/AC, NiMo/TiO₂, and NiMo/AC-TiO₂ materials are mesoporous.

Results for the textural properties of NiMo/AC100, NiMo/AC200,NiMo/AC300, and NiMo/AC400 are presented in Table. 3 In addition to thefact that the textural properties of the carbon support changed uponloading the supports with metal catalysts, analysis of the results showthat there is a correlation between the textural property and thecalcination temperature at which the prepared catalysts were treatedafter impregnation. NiMo/AC400 has the largest BET surface area of 434.5m²/g, which is significantly greater when compared with surface areas of323, 352, and 356 m²/g obtained for NiMo/AC100, NiMo/AC200, andNiMo/AC300, respectively. A similar trend is observed for the externalsurface area, micropore area, as well as the pore volumes of thesupported HDS catalyst. The observation may be resulted from the factthat more effective evacuation of the adsorbed H₂O molecule trappedwithin the pores of the carbon support.

TABLE 3 Textural Properties of Catalysts: NiMo/AC100, NiMo/AC200 andNiMo/AC300 NiMo/AC400 BET External Total pore Average Surface SurfaceMicropore volume of pore Area Area Area pores diameter Catalysts (m²/g)(m²/g) (m²/g) (cm³/g) (Å) NiMo/AC100 323.0251 220.0663 102.9588 0.52960965.5811 NiMo/AC200 356.6956 229.1308 127.5647 0.548710 61.5325NiMo/AC300 352.1114 230.7778 121.3336 0.530329 60.2456 NiMo/AC400434.5335 259.5915 174.9420 0.595631 54.8295

The N₂ adsorption-desorption isotherms for NiMo/AC100, NiMo/AC200,NiMo/AC300, and NiMo/AC400 are presented in FIGS. 7, 8, 9, and 10,respectively. The shapes of the isotherms are similar and match the typeIV isotherms unique to the mesoporous material. Moreover, the averagepore size (Table 4) of all the catalysts fall within the range of 2 nmto 50 nm. The average pore size recorded for NiMo/AC100, NiMo/AC200,NiMo/AC300, and NiMo/AC400 are 66 Å (6.6 nm), 62 Å (6.2 nm), 60 Å (6.0nm), and 55 Å (5.5 nm), respectively. It is important to note that thereis a decrease in the average pore size of the catalysts as thecalcination temperature increases from 100 to 400° C. Though thedifference in pore size might seem small, the difference becomessignificant when the pore size of NiMo/AC400 is compared with othersincluding NiMo/AC100, NiMo/AC200, and NiMo/AC300.

Results for the textural properties of NiMo/AC(U-S), NiMo/AC(CA), andNiMo/AC(EDTA) are presented in Table 4. The textural properties of thecarbon support changed upon loading the supports with metal catalysts,similar to the cases of other catalysts discussed in the previoussections. Analysis of the results shows that there are differences inthe measured BET surface area, external surface area, micropore area,and pore volume of the catalyst. NiMo/AC(EDTA) has the largest BETsurface area of 342 m²/g, compared to BET surface values of 278 and 288m²/g recorded for NiMo/AC(U-S) and NiMo/AC(CA), respectively. A similartrend is observed for the external surface area, micropore area, as wellas pore volumes of the three supported HDS catalysts. The observeddifferences could be due to the fact that the chelating agents, CA andEDTA could be more effectively evacuated from the surface of the poresthan adsorbed water.

TABLE 4 Textural Properties of Catalysts: NiMo/AC(U- S), NiMo/AC(CA) andNiMo/AC (EDTA) BET External Total pore Average Surface Surface Microporevolume of pore Area Area Area pores diameter Catalysts (m²/g) (m²/g)(m²/g) (cm³/g) (Å) NiMo/AC(U-S) 278.7802 215.0349 85.7453 0.45323261.1136 NiMo/AC(CA) 288.7802 205.0349 83.7453 0.441932 61.2136NiMo/AC(EDTA) 342.8653 235.5285 107.3368 0.485952 56.6930

Besides the changes observed in the surface area and pore volumes of theprepared catalysts when compared to the activated carbon support, thereare noticeable changes in the pore size of the materials. The porediameter of the activated carbon support was 5.2 nm compared to the 5.7,6.1 and 6.1 nm recorded for NiMo/AC(U-S), NiMo/AC(CA) and NiMo/AC(EDTA)respectively. The average pore diameters of NiMo/AC(CA) andNiMo/AC(EDTA) are the same but larger than the average pore diameter ofNiMo/AC(U-S). This is an indication that both CA and EDTA had similareffects on the textural properties of the prepared catalysts and theirimpacts might be different compared to the use of ultrasonication. Inall cases, the average pore diameters of the catalysts are between therange of 2-50 nm and it shows that the materials are mainly mesoporous.It is evident from the shape of the N₂ adsorption-desorption isothermspresented in FIGS. 11, 12, and 13, that the three catalysts aremesoporous as the shapes are similar to the type IV isotherms peculiarto the mesoporous material.

Example 12 FT-IR Results

The FTIR spectra shown in FIGS. 14 and 15 reveal some of the functionalgroups present in the supported catalysts. The most conspicuous are thebands centered around 3400, 2350, 1600 and 1300-100 cm⁻¹. The broad bandcentered at 3400 cm⁻¹ is peculiar to the stretching (O—H) vibration incompounds with hydroxyl groups while the band at 2350, 1600 and 1300-100cm⁻¹ are unique to the CC stretching vibration in alkyne group, (C═O)stretching vibrations of carboxylic and carbonyl compounds. This is aclear indication of the presence of acidic oxygen groups that can serveas adsorption sites on the surface of the catalysts. Peaks can beattributed to the Mo—O—Mo stretching vibrations are found at 620 and 850cm⁻¹ while the band at 797 cm⁻¹ can be conveniently attributed to thepresence of the polymobdate species, Mo₃₆.

Example 13 XRD Results

The powder X-ray diffraction results for the catalysts NiMo/AC100,NiMo/AC200, NiMo/AC300 and NiMo/AC400 are presented in FIG. 16. Thediffractograms are stacked for ease of comparison. In all cases, thereare three major broad diffraction peaks at 2θ values of 25°, 37° and54°. However, the peaks for NiMo/AC300 and NiMo/AC400 are more intensewhen compared to NiMo/AC100 and NiMo/AC200. The appearance of thesepeaks can be attributed to presence of Mo species and the varying degreeof intensity of the peaks is a result of the difference in degree ofcrystallinity. This is an indication that the calcination at highaffects the degree of crystallinity of Mo incorporated into the carbonsupport. The other peaks are broad and barely visible but the mostconspicuous diffraction peak at around 2θ 25° can be attributed to thehexagonal MoO₃ [C. Fontaine, Y. Romero, A. Daudin, E. Devers, C. Bouchy,and S. Brunet, “Insight into sulphur compounds and promoter effects onMolybdenum-based catalysts for selective HDS of FCC gasoline,” Appl.Catal. A Gen., vol. 388, no. 1-2, pp. 188-195, 2010; A. Tougerti, E.Berrier, A. S. Mamede, C. La Fontaine, V. Briois, Y. Joly, E. Payen, J.F. Paul, and S. Cristol, “Synergy between XANES Spectroscopy and DFT toElucidate the Amorphous Structure of Heterogeneous Catalysts:TiO2-Supported Molybdenum Oxide Catalysts,” Angew. Chemie-Int. Ed., vol.52, no. 25, pp. 6440-6444, 2013; and T. Bhaskar, K. R. Reddy, C. P.Kumar, M. R. V. S. Murthy, and K. V. R. Chary, “Characterization andreactivity of molybdenum oxide catalysts supported on zirconia,” Appl.Catal. A Gen., vol. 211, no. 2, pp. 189-201, 2001, each incorporatedherein by reference in their entirety]. Diffraction peaks at 2θ values20°-30° (002) 40° to 50° (101) have been reported for the graphite phaseof activated carbon [L. J. Konwar, P. Maki-Arvela, E. Salminen, N.Kumar, A. J. Thakur, J. P. Mikkola, and D. Deka, “Towards carbonefficient biorefining: Multifunctional mesoporous solid acids obtainedfrom biodiesel production wastes for biomass conversion,” Appl. Catal. BEnviron., vol. 176-177, pp. 20-35, 2015; S. Kang, J. Ye, and J. Chang,“Recent Advances in Carbon-Based Sulfonated Catalyst: Preparation andApplication,” Int. Rev. Chem. Eng., vol. 5, no. 2, pp. 133-144, 2013;and X. Y. Liu, M. Huang, H. L. Ma, Z. Q. Zhang, J. M. Gao, Y. L. Zhu, X.J. Han, and X. Y. Guo, “Preparation of a carbon-based solid acidcatalyst by sulfonating activated carbon in a chemical reductionprocess,” Molecules, vol. 15, no. 10, pp. 7188-7196, 2010, eachincorporated herein by reference in their entirety]. The additionalpeaks can be attributed to the other forms MoO₃ or even MoO₂. Thereforethe presence of these peaks can be taken as additional evidence ofsuccessful impregnation of the carbon support with the metal catalyst.There are no visible and peculiar peaks that indicate the presence ofand Ni due to the low concentration of the promoter compared to theproportion Mo [A. Omri and M. Benzina, “Influence of the origin ofcarbon support on the structure and properties of TiO₂ nanoparticlesprepared by dip coating method,” Arab. J. Chem., 2015, incorporatedherein by reference in its entirety].

Example 14 SEM and EDX Results

The scanning electron microscopy (SEM) images in FIGS. 17 and 18 showsurface morphology and textural characteristics of selected catalysts.It is important to note that the particles do not have a regular shape,which is a common feature of activated carbon and other amorphousmaterials used as adsorbent or catalysts support [Y. Wang and R. T.Yang, “Desulfurization of liquid fuels by adsorption on carbon-basedsorbents and ultrasound-assisted sorbent regeneration,” Langmuir, vol.23, no. 7, pp. 3825-3831, 2007, incorporated herein by reference in itsentirety]. Other porous materials like MOFs SBA-15 are often used assupport and adsorbents with characteristic shapes and distinctmorphology. It is obvious that some of the pores on the surface of theactivated carbon support and metal particles on the surface arevisible—an indication that some of the metals got deposited onto thesurface of the carbon support and the others might be trapped inside thepores. FIG. 19 is an energy dispersive x-ray (EDX) spectrum. Table 5provides both qualitative and quantitative information on the surfacecomposition of the prepared catalysts. The identified elements presenton the catalysts include carbon, oxygen, molybdenum, cobalt, and nickel.As the main component of the support material, it was not unexpectedthat carbon has the most intense peak and it represents over sixtypercent of the elements. The peaks for oxygen and molybdenum are alsoconspicuous and account for approximately nine percent and sevenpercent, respectively. The above analysis is a clear indication that Mo,Co, and Ni in the form of nanoparticles were successfully incorporatedonto the activated carbon support.

TABLE 5 Distribution of elements on the surface of the NiMo/AC LineApparent k Wt % Element Type Concentration Ratio Wt % Sigma C K series66.46 0.66463 81.81 0.54 O K series 5.89 0.01982 9.02 0.49 Ni K series3.55 0.03547 1.52 0.13 Zr L series 0.00 0.00000 0.00 0.00 Mo L series17.10 0.17096 7.64 0.27 Total: 100.00

Example 15 HDS Activity of Catalysts: Nature of Support Materials andHDS Activity

The catalytic performance of the prepared catalysts towardsdesulphurization of DBT for the reactions conducted in a pressure batchreactor is summarized in Table 6 and FIG. 20. In all cases, a continuousdecrease in the concentration of DBT in the model fuel was observed asreactions progressed. There was a decrease in the concentration of DBTeven at the zeroth hour when sampling begins, an indication that thehydrodesulphurization reaction starts before the reaction temperaturereaches the desired set point of 350° C. Earlier reports have shown thatHDS of DBT is feasible even at a lower temperature of 300° C. using theMo based catalysts supported on carbon [H. Farag, I. Mochida, and K.Sakanishi, “Fundamental comparison studies on hydrodesulfurization ofdibenzothiophenes over CoMo-based carbon and alumina catalysts,” Appl.Catal. A Gen., vol. 194-195, pp. 147-157, March 2000, incorporatedherein by reference in its entirety].

TABLE 6 HDS Test Results: performance of NiMo/AC, NiMo/TiO₂, andNiMo/AC-TiO₂ Concentration of DBT in Products Sampled at intervals (ppm)Set Point Catalysts (0 h) 1 h 2 h 3 h NiMo/AC 740 491 266 109 NiMo/TiO₂607 465 391 228 NiMo/AC-TiO₂ 795 423 220 62

When comparing the concentrations of DBT in samples collected at thesame interval for the three catalysts, it was observed that theconcentrations are not the same. The concentration of the DBT wasconsistently lower in the case of NiMo/AC than when NiMo/TiO₂ andNiMo/AC-TiO₂ were used as catalysts for the HDS reaction. Suchdifference in catalytic performance can be attributed to the nature ofthe support material as the amount of Ni and Mo on the support materialsremain the same. The obvious advantage of the carbon material over TiO₂is its larger surface area and a different pore structure. Previousstudies have shown that higher conversions could be achieved usingmaterials with larger surface areas [M. Kouzu, Y. Kuriki, F. Hamdy, K.Sakanishi, Y. Sugimoto, and I. Saito, “Catalytic potential ofcarbon-supported NiMo-sulfide for ultra-deep hydrodesulfurization ofdiesel fuel,” Appl. Catal. A Gen., vol. 265, no. 1, pp. 61-67, 2004; N.Escalona, J. Ojeda, J. M. Palacios, M. Yates, J. L. G. Fierro, A. L.Agudo, and F. J. Gil-Llambias, “Promotion of Re/Al₂O₃ and Re/C catalystsby Ni sulfide in the HDS and HDN of gas oil: Effects of Ni loading andsupport,” Appl. Catal. A Gen., vol. 319, pp. 218-229, 2007; H. Farag, D.D. Whitehurst, K. Sakanishi, and I. Mochida, “Carbon versus Alumina as aSupport for Co—Mo Catalysts Reactivity towards HDS of Dibenzothiophenesand Diesel Fuel,” Catal. Today, vol. 50, no. 1, pp. 9-17, 1999, eachincorporated herein by reference in their entirety]. Moreover,comparison study on carbon materials and metal oxides has shown thatcarbon materials with a large surface performed better than TiO₂ andAl₂O₃ [P. Gheek, S. Suppan, J. Trawczyński, A. Hynaux, C. Sayag, and G.Djega-Mariadssou, “Carbon black composites-supports of HDS catalysts,”Catal. Today, vol. 119, no. 1-4, pp. 19-22, 2007; and P. A. Nikulshin,N. N. Tomina, A. A. Pimerzin, A. V. Kucherov, and V. M. Kogan,“Investigation into the effect of the intermediate carbon carrier on thecatalytic activity of the HDS catalysts prepared usingheteropolycompounds,” Catal. Today, vol. 149, no. 1-2, pp. 82-90, 2010,each incorporated herein by reference in their entirety]. Anotherimportant observation is that when comparing the performance ofNiMo/TiO₂ to NiMo/AC-TiO₂, a lower concentration of DBT was recorded forNiMo/AC-TiO₂ at all the time intervals. Thus, it is clear that thecarbon from waste tires is a more effective support material for Ni andMo when compared to TiO₂ and composite material AC-TiO₂.

HDS rate constants k (s⁻¹), k (s⁻¹ g⁻¹ cat.) and R² values werecalculated for NiMo/AC, NiMo/TiO₂, and NiMo/AC-TiO₂ and presented inTable 7 and FIG. 21. The magnitude of the R² values ranges from 0.850 to0.989, an indication that the reactions involving all the testedcatalysts agree well with the proposed pseudo-first order kinetics forthe desulfurization process using supported Mo catalysts [J. Chen, H.Yang, and Z. Ring, “HDS kinetics study of dibenzothiophenic compounds inLCO,” in Catalysis Today, 2004, vol. 98, no. 1-2 SPEC. ISS., pp.227-233, incorporated herein by reference in its entirety]. Calculationsfor the nth order rates yielded lower R² values. The results also show astrong correlation between the performance of the catalysts towards thedesulfurization of DBT and the magnitude of the pseudo 1^(st) order rateconstants. For example, the HDS rate constant for NiMo/AC(EDTA),NiMo/AC(CA), NiMo/AC(U-S), and NiMo/AC are 2.3×10⁻⁴ s⁻¹, 1.8×10⁻⁴ s⁻¹,1.6×10⁻⁴ s⁻¹, and 1.5×10⁻⁴ s⁻¹, respectively. The difference in themagnitude of HDS rate constants reflects the relative performance ofcatalysts, and thus providing insight into the activity of the preparedcatalysts. It is clear that NiMo/AC(EDTA) is the most effective amongthe prepared and tested catalysts in catalyzing degradation reaction ofDBT. The magnitude of the HDS rate constants also indicates that thechelating agents are more effective in the dispersion of active metalspecies when compared to ultrasonication.

TABLE 7 Kinetic parameters: HDS rate constants for NiMo/AC, NiMo/TiO₂,and NiMo/AC-TiO₂ 1^(st) Order Kinetics Rate Constants k_(HDS) k_(HDS) ×10⁴ k_(HDS) × 10⁴ Catalysts (s⁻¹) (s⁻¹) (s⁻¹g⁻¹cat) R² NiMo/AC 2.0E−042.0E+00 6.58 0.988 NiMo/TiO₂ 1.0E−04 1.00 3.33 0.965 NiMo/AC-TiO₂1.7E−04 1.73 5.75 0.985

Example 16 HDS Activity of Catalysts: Effects of Calcination Temperature

The results in Table 8 and FIG. 22 demonstrate the concentration ofsulfur present in the model at various time intervals during thereaction using different catalysts NiMo/AC100, NiMo/AC200 andNiMo/AC300, or NiMo/AC400. Different concentrations of sulfur at thesame time intervals using the catalysts calcined at differenttemperatures are an indication that the activity of the catalysts wasalso affected by the thermal treatment. Considering the concentrationprofiles of the products collected at different hours of theexperiments, it is clear that catalysts calcined at 100° C. and 200° C.are more effective in the HDS of DBT. There is a significant differencebetween the sulfur concentration of products collected at the samereaction time for the catalysts prepared from the same materials andunder similar conditions except for calcination temperature. Thus, itwould be rational to attribute the difference in activity of thecatalysts to modifications that occur during the calcination process.Some functionalities and features that facilitate the operation of thecatalyst may be lost at a higher calcination temperature. Recent studieson SBA-15 supported NiMo showed that higher activity could be achievedwhen catalysts were calcined at 300° C. rather than at highertemperatures [S. A. Ganiyu, K. Alhooshani, and S. A. Ali, “Single-potsynthesis of Ti-SBA-15-NiMo hydrodesulfurization catalysts: Role ofcalcination temperature on dispersion and activity,” Appl. Catal. BEnviron., vol. 203, pp. 428-441, 2017, incorporated herein by referencein its entirety]. It is noted that the two catalysts, CMAC and NMAC,also performed better with treatment at 300° C. The two catalysts showedinsignificant difference in activity when they were calcined at the sametemperature.

TABLE 8 HDS test results: performance of NiMo/AC100, NiMo/AC200,NiMo/AC300, and NiMo/AC400 Concentration of DBT in of products taken atintervals (ppm) Set point Catalysts (0 h) 1 h 2 h 3 h NiMo/AC100 713 546112 49 NiMo/AC200 740 512 122 60 NiMo/AC300 882 658 385 147 NiMo/AC400840 691 366 153

The HDS rate constants k (s¹), ks⁻¹ g⁻¹ cat. R² values were calculatedfor all the prepared catalysts including NiMo/AC100, NiMo/AC200,NiMo/AC300, and NiMo/AC400, and the results are presented in Table 9.The values were determined using the initial conversion values obtainedafter the first hour of the reaction. The magnitude of R² values rangesfrom 0.850 to 0.989, indicating that the reactions involving all thetested catalysts agree well with the proposed pseudo-first orderkinetics for the desulfurization process using supported Mo catalysts.Calculations for the nth order rates yielded lower R² values.

A similar trend is observed in the relative magnitude of the catalystssubjected to thermal treatments at different temperatures prior to thereduction, presulfidation, and the subsequent HDS activity tests asdescribed in the previous sections. The pseudo 1^(st) order rateconstant calculated for NiMo/AC100, NiMo/AC200, NiMo/AC300, andNiMo/AC400 are 2.0×10⁻⁴ s⁻¹, 1.9×10⁻⁴ s⁻¹, 8.8×10⁻⁵ s⁻¹, and 8.9×10⁻⁵s⁻¹, respectively (FIGS. 23A-D). The decrease in the magnitude of therate constant with increasing calcination temperature is a clearindication that calcination at higher temperatures reduces the activityof the catalyst. The observed phenomenon can be attributed to theenhanced crystallinity of the active species as shown in XRD spectra.

TABLE 9 Kinetic parameters: HDS rate constants for NiMo/AC 100,NiMo/AC200, NiMo/AC300, and NiMo/AC400 1^(st) Order Kinetics Constantsk_(HDS) k_(HDS) × 10⁴ k_(HDS) × 10⁴ Catalysts (s⁻¹) (s⁻¹) (s⁻¹g⁻¹cat) R²NiMo/AC100 2.0E−04 1.52 5.05 0.972 NiMo/AC200 1.9E−04 1.9E+00 6.18 0.997NiMo/AC300 8.8E−05 0.88 2.92 0.980 NiMo/AC400 8.9E−05 0.89 2.97 0.989

Example 17 HDS Activity of Catalysts: Effects of Ultrasonication andChelating Agents

The results of HDS activity tests for all materials are presented inTable 10. Analysis of the results shows that there is a significantdifference in the performance of each catalyst towards the HDS of DBT(FIG. 24). It is evident that NiMo/AC(EDTA) is the most effectivecatalyst among the three in the NiMo series. The concentration of sulfuris reduced to less than 10 ppm for the reaction involving NiMo/AC(EDTA)while the concentration of sulfur in aliquots obtained using NiMo/AC(CA)or NiMo/AC(U-S) was above 50 ppm at the same time interval. Comparisonof the sulfur concentration in aliquots from reactions involvingNiMo/AC(CA) and NiMo/AC(U-S) reveals that more efficient DBT HDS wasachieved with catalysts prepared using citric acid rather thanultrasonication for enhanced dispersion. Analysis on the CoMo/AC seriesshowed a similar performance pattern while the concentrations of sulfurin all the aliquots were much lower compared to the NiMo/AC. Forexample, the concentration of sulfur was reduced to below detectablelimit using CoMo/AC(CA), while the concentration was above 5 ppm in thecase of the reactions involving NiMo/AC(EDTA) at the third hour. Theobserved trend is an indication that EDTA is more effective indispersing the active phase compared to ultrasonication or citric acid.

TABLE 10 HDS test results: performance of MAC, NMAC, and CMAC catalystsConcentration of DBT in products taken at intervals (ppm) Set pointCatalysts (0 h) 1 h 2 h 3 h NiMo/AC(U-S) 520 359 305 78 NiMo/AC(CA) 703377 166 75 NiMo/AC(EDTA) 634 364 141 36

Results for the kinetics study of NiMo/AC(U-S), NiMo/AC(CA), andNiMo/AC(EDTA) are presented in Table 11. HDS rate constants k (s⁻¹),ks⁻¹ g⁻¹ cat. and R² values were calculated for the three catalysts. Themagnitude of the R² values ranges from 0.850 to 0.989, an indicationthat the reactions involving all the tested catalysts agree well withthe proposed pseudo-first order kinetics for the desulfurization processusing supported Mo catalysts. Calculations for the nth order ratesyielded lower R² values. The results also show a strong correlationbetween the performance of the catalysts towards the desulfurization ofDBT and the magnitude of the pseudo 1^(st) order rate constants. Forexample, the HDS rate constant for NiMo/AC(EDTA), NiMo/AC(CA),NiMo/AC(U-S), and NiMo/AC are 2.3×10⁻⁴ s⁻¹, 1.8×10⁻⁴ s⁻¹, 1.6×10⁻⁴ s⁻¹,and 1.5×10⁻⁴ s⁻¹, respectively (FIGS. 25A-C). The differences in themagnitude of HDS rate constants reflect the relative performance of thecatalysts, and provide more insight into the activity of the preparedcatalysts. It is now clear that NiMo/AC(EDTA) is the most effective ofthe prepared and tested catalysts for degradation of DBT. The magnitudeof the HDS rate constants also indicates that the chelating agents aremore effective in dispersing active metal species compared toultrasonication.

TABLE 11 Kinetic parameters: HDS rate constants for NiMo/AC(U- S),NiMo/AC(CA), and NiMo/AC(EDTA) 1^(st) Order Kinetics Constants k_(HDS)k_(HDS) × 10⁴ k_(HDS) × 10⁴ Catalysts (s⁻¹) (s⁻¹) (s⁻¹g⁻¹cat) R²NiMo/AC(U-S) 1.6E−04 1.6E+00 5.22 0.921 NiMo/AC(CA) 1.8E−04 1.84 6.150.850 NiMo/AC(EDTA) 2.3E−04 2.26 7.53 0.981

Example 18 CONCLUSIONS

A family of Mo based catalysts supported on activated carbon derivedfrom waste tires, TiO₂, and AC-TiO₂ composites were prepared and appliedin the HDS of DBT. The catalysts were characterized by varioustechniques including N₂-physisorption, X-ray diffraction (XRD), andFT-IR. The HDS activity of the catalyst was tested in a pressure batchreactor using decalin spiked with dibenzothiophene as model fuel. Theactivity of the catalyst was found to be dependent on the compositionsof catalysts and support materials as well as the preparation methods.

The activated carbon support was found to be the most effective for thecatalysts when compared with TiO₂ and AC-TiO₂ composite supports.Results from the characterization and the catalytic activity tests showthat chelating agents were more effective in the dispersion of theactive phase and the highest HDS activity was observed when EDTA wasused.

Direct desulfurization was achieved using the Mo based catalysts, andthe most efficient reaction route and desulfurization of the DBT wasachieved with NiMo/AC, especially when EDTA was used to aid thedispersion of the active phase.

1. A method of producing a Ni/Mo hydrodesulfurization catalyst, themethod comprising: dissolving an Ni(II) salt in water to form a firstsolution; dissolving an Mo(VI) salt in water to form a second solution;mixing an activated carbon with the first and second solutions to form amixture; drying the mixture at a temperature of 50-150° C. therebyproducing a solid; then calcining the solid at a temperature of 160-500°C. to form the Ni/Mo hydrodesulfurization catalyst, wherein: the Ni/Mohydrodesulfurization catalyst comprises nickel and molybdenum disposedon the activated carbon; the Ni/Mo hydrodesulfurization catalyst ismesoporous with a BET surface area of 250-500 m²/g, an average porediameter of 4-10 nm, and a pore volume of 0.2-3 cm³/g; and the Mo(VI)salt is ammonium heptamolybdate(VI).
 2. (canceled)
 3. The method ofclaim 1, wherein the Ni/Mo hydrodesulfurization catalyst is calcined ata temperature of 160-200° C.
 4. The method of claim 1, wherein themixture further comprises a chelating agent which isethylenediaminetetraacetic acid, citric acid, or both.
 5. The method ofclaim 1, further comprising subjecting the mixture to ultrasonication.6. The method of claim 1, further comprising granulating and pyrolyzingwaste tires to form the activated carbon.
 7. The method of claim 1,wherein the activated carbon has a BET surface area of 500-700 m²/g, anaverage pore diameter of 3-8 nm, and a pore volume of 0.25-4 cm³/g. 8.The method of claim 1, wherein the Ni/Mo hydrodesulfurization catalysthas an activated carbon content in a range of 60-95% by weight relativeto a total weight of the Ni/Mo hydrodesulfurization catalyst.
 9. Themethod of claim 1, wherein the Ni(II) salt is nickel(II) acetate. 10.(canceled)
 11. The method of claim 1, wherein the Ni/Mohydrodesulfurization catalyst has a Ni:Mo molar ratio in a range of 1:10to 1:2.
 12. The method of claim 1, wherein the Ni/Mohydrodesulfurization catalyst has a Mo content in a range of 4-20% byweight relative to a total weight of the Ni/Mo hydrodesulfurizationcatalyst. 13-20. (canceled)